Throat diameter question

[ratbuster]

Match chambers I have seen are usually spec'd at .0005" larger than the bullet. I had a custom reamer made which was also spec'd at one half thou over bullet diameter. After I got the barrel I did a chamber cast and the throat is .0004 smaller (.2431) than the print called for. Bottom line is there is only about 2 ten thousandths clearance between throat and bullet. I like the idea of minimal clearance between the two but have no experience with one that tight. Of course the target will give me the answer but I'm curious what others may have found in a situation like this.

 

[Stan Taylor]

Well first thing I would do is take a good set of 1 inch mikes an measure the throat part of reamer if you have good measures I would send the reamer back I would prefer 243.8 on free bore.

 

[Will Henry]

I have used throats which had as little as .0001 clearance and they worked just fine unless I got some bullets which were big. In one case, I built a 303 British with a .3115" throat which worked very well with Sierra bullets which measured .3112-.3113. The next bunch of sierras measured .3116-.3117 and would stick in the throat before contacting the lands. By the way, when a bullet is advertised as being .311, I expect and can accept some variation. By the time the bullet is exceeding a half thou large though, I think it should be advertised as being .3115; especially a match bullet. WH